Wheatstone bridge & strain gauges worksheet with answers

Free printable Wheatstone bridge & strain gauges worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
+−2 VR1​ = 50 ΩR2​ = 300 ΩR3​ = 400 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 50 Ω, R₂ = 300 Ω and R₃ = 400 Ω. Find the unknown resistor R4.

R1 = 50 ΩR2 = 300 ΩR3 = 400 Ω
R4 = Ω
2.Easy
+−15 VR1​ = 200 ΩR2​ = 500 ΩR3​ = ?R4​ = 100 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 200 Ω, R₂ = 500 Ω and R₄ = 100 Ω. Find the setting R3.

R1 = 200 ΩR2 = 500 ΩR4 = 100 Ω
R3 = Ω
3.Medium
+−15 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−Vab​ = ?

A bridge has four 300 Ω arms and Vs = 15 V. The sensor R₂ increases by ΔR = 0.6 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 15 VR = 300 ΩΔR = 0.6 Ω
Vab = mV
4.Medium
+−2 V350 Ω350 Ω350 Ω350 Ωab+−

A 350 Ω strain gauge is one arm (R₂) of a bridge with four equal 350 Ω arms and an excitation of 2 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 2 VR = 350 Ω
Pg = mW
5.Hard
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 3 V. The largest strain to be measured is 400 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 3 VGF = 2εmax = 400 µεVFS = 3.3 V
G =
6.Hard
+−10 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω + ΔR1000 Ω − ΔRab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 10 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 1500 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2ε = 1500 µε
Vo = mV

Answer key

  1. 1. R4 = 2400 Ω
  2. 2. R3 = 40 Ω
  3. 3. Vab = 7.5 mV
  4. 4. Pg = 2.857 mW
  5. 5. G = 5500
  6. 6. Vo = 30 mV

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